1. Field of the Invention
The invention relates to a timepiece (watch and clock) for displaying at least either of time information such as an hour, minute, and second, or calendar information such as a date, days of the week, a month, and a year by use of a liquid crystal display panel, and more particularly, to not only a timepiece for indicating digital display of time information and calendar information but also a combination timepiece capable of indicating digital display and analog display of time information by hands, or an analog timepiece for displaying markers and so forth on a dial thereof utilizing a liquid crystal display panel, or for indicating simulated hands for an hour hand, a minute hand, and a second hand.
2. Description of the Related Art
A timepiece for indicating digital display of time information such as the hour, minute, and second, and calendar information such as the date, days of the week, the month, and the year, by use of a liquid crystal display panel, has been in widespread use for wrist watches and clocks, provided with a crystal oscillation circuit.
There has also been in use a combination watch wherein an analog display indicating time information by the hands of the watch is used in combination with digital display indicating time information and calendar information in numbers and letters.
Further, there has been proposed an analog watch for selectively displaying markers in various patterns, or for displaying simulated hands for an hour hand, a minute hand, and a second hand, by providing the dial thereof based on a liquid crystal display panel (refer to, for example, Japanese Patent Laid-open S54-153066).
In a conventional liquid crystal display panel for displaying time information and calendar information, used in such a watch or clock, a liquid crystal cell filled with liquid crystals is sandwiched between two transparent substrates having an electrode on respective inner surfaces thereof, facing each other, and an upper polarizing film and a lower polarizing film are disposed, respectively, on the external surface of the transparent substrates, on the opposite sides. If an electric field is applied to the liquid crystals by applying a voltage to a pair of electrodes on the transparent substrates holding the liquid crystal cell therebetween, the optical property of the liquid crystals is changed, thereby locally controlling transmission and absorption of light falling on the liquid crystal display panel such that a predetermined display is effected.
Either of the upper polarizing film or the lower polarizing film is a polarizing film absorbing the light linearly polarized in a direction orthogonal to the transmission axis thereof.
In the case of a watch using the conventional liquid crystal display panel described above, time information and calendar information are displayed in black against a white background in a normally white mode that is common.
However, by simply displaying time information and calendar information in black against the white background, as described in the foregoing, neither variation in design nor interest can be offered, with a resulting tendency to lose soon popularity with consumers. Probably, as a result, consumption of digital watches has recently been on the decline, and neither combination watches nor analog watches with a liquid crystal display panel have since received market acceptance.
In light of the present situation as described, the invention has been developed, and an object thereof is to provide a timepiece (watch and clock) capable of providing attractive variation in design while indicating digital display or analog display by use of a liquid crystal display panel.
To this end, the invention provides a timepiece provided with a liquid crystal display panel, capable of displaying at least either of time information or calendar information, and the liquid crystal display panel is made up as follows.
A liquid crystal cell with liquid crystals sealed thereinbetween is sandwiched between two transparent substrates having an electrode on each of inner surfaces thereof, facing each other, and a light absorption film that is disposed on the side of one of the polarizing sheets opposite from the liquid crystal cell.
For each of the polarizing sheets, a sheet (reflection-type polarizing sheet or polarizing film) reflecting the light linearly polarized in the direction orthogonal to the transmission axis thereof is used.
It is desirable that the polarizing sheets disposed on the opposite sides of the liquid crystal cell be arranged such that the transmission axes of the respective polarizing sheets cross each other at right angles, or run in parallel with each other.
Further, liquid crystals causing linearly polarized light passing therethrough to undergo phase modulation or intensity modulation are sealed in the liquid crystal cell. There are available twisted nematic liquid crystals, ferroelectric or anti-ferroelectri liquid crystals, and so forth as the liquid crystals causing phase modulation to occur, while there are available guest host liquid crystals as the liquid crystals causing intensity modulation to occur. However, twisted nematic liquid crystals having a twist angle of not more than 90 degrees may be used as well.
It is desirable that one of the polarizing sheets, disposed on the visible side of the liquid crystal cell, is arranged such that the transmission axis thereof is aligned in the direction of, or in the direction orthogonal to, the long axes of liquid crystal molecules in the liquid crystal cell, on the visible side thereof.
The timepiece according to the invention, constructed as above, is capable of indicating display in a metallic color by controlling whether all light incoming from the visible side (the upper side) of the liquid crystal cell is reflected, or a half of the light is reflected.
Depending on whether the transmission axes of the polarizing sheets, disposed on the opposite sides of the liquid crystal cell, respectively, cross each other at right angles or run in parallel with each other, whether the transmission axis of one of the polarizing sheets, disposed on the visible side of the liquid crystal cell, is aligned in the direction of or in the direction orthogonal to, the long axes of the liquid crystal molecules in the liquid crystal cell, on the visible side thereof, or depending on the types of liquid crystals in use or the method of applying voltage, either of the background part or display segment can be displayed in a metallic color through full reflection of incoming light while the other can be displayed in the color of the light absorption film.
For example, with the use of a liquid crystal display panel wherein the polarizing sheets disposed above and below the liquid crystal cell, respectively, are arranged such that the transmission axes thereof run in parallel with each other, and the liquid crystal cell with twisted nematic liquid crystals having a twist angle of 90 degrees sealed therein is used, half of the light falling on the liquid crystal cell from the visible side thereof (above) is reflected by the polarizing sheet on the upper side. The other half of the light is transmitted through the liquid crystal cell and, in the background part of the liquid crystal display panel, where no voltage is applied to the liquid crystals of the liquid crystal cell, is rotated by 90 degrees. Consequently, transmitted light is turned into the light linearly polarized in the direction orthogonal to the transmission axis of the polarizing sheet disposed on the lower side, thereby being reflected in full by a polarizing sheet on the lower side. As a result, the background part is displayed in a metallic color (like a mirror).
Meanwhile, in the display segment of the liquid crystal cell for displaying time information and calendar information, where a voltage is applied to the liquid crystals, light transmitted through the liquid crystals is not rotated, and is turned to the light linearly polarized in the direction parallel with the direction of the transmission axis of the polarizing sheet on the lower side, thus being allowed to pass through the polarizing sheet on the lower side to be absorbed by the light absorption film. Consequently, the display segments are displayed in a black color.
If a colored material is used for the light absorption film, light only in a specific color is reflected, and the light reflected is transmitted through the polarizing sheet on the lower side, the liquid crystal cell, and the polarizing sheet on the upper side, in reverse order, falling on the visible side, and indicating display in the color of the light absorption film. In this case, however, since half of the incoming light is reflected by the polarizing sheet on the upper side, the entire surface of the liquid crystal display panel indicates display in a somewhat metallic tone.
Further, it is also possible to display the background part in the color of the light absorption film and to display the display segment in a metallic color by inverting the mode of display as described above.
Accordingly, with the timepiece according to the invention, time information and calendar information can be displayed in a fresh and variable fashion in marked contrast with the conventional timepiece for indicating display of time information and calendar information in a black color against a white background, thereby enabling variation in design to be brought about, and offering a sense of amusement.
Furthermore, with the timepiece according to the invention, wherein a backlight is installed in place of the light absorption film, display by light from the backlight can be effected at night or in dark locations.
If a translucent absorbing film is installed between the backlight and one of the polarizing sheets, adjacent thereto, transmission-type display using light from the backlight as well as reflective-type display using external light can be made easier for a viewer.
Further, if a polarizing film (absorption type) for absorbing the light linearly polarized light in the direction orthogonal to the transmission axis thereof is disposed on the external side of one of the polarizing sheets, disposed on the visible side of the liquid crystal cell of the liquid crystal display panel, so that the transmission axis of the polarizing film is oriented substantially in the same direction as the transmission axis of the polarizing sheet described above, the outgoing quantity of light reflected from across the surface of the polarizing sheet on the upper side is reduced, moderating the metallic gloss (luster) across the surface of the display segment, and enabling a viewer to see the display with greater ease while improving the viewing angle characteristic of the liquid crystal display panel as well.
In this case, by use of a color polarizing film capable of mainly absorbing a light Component at a specific wavelength, out of the light linearly polarized light in the direction orthogonal to the transmission axis thereof as the polarizing film, the metallic gloss (luster) across the surface of the display segment can be moderated without sacrificing much brightness of display.
Otherwise, if a light diffusion layer in place of the polarizing film is installed on the external side of one of the polarizing sheets, disposed on the visible side of the liquid crystal cell of the liquid crystal display panel, light reflected from across the surface of the polarizing sheet on the upper side is diffused, moderating the metallic gloss, and providing a softer display while improving the viewing angle characteristic of the liquid crystal display panel as well.
Furthermore, in the timepiece according to the invention described in the foregoing, in place of the reflective polarizing sheet disposed on the visible side of the liquid crystal cell of the liquid crystal display panel, an absorption-type polarizing sheet may be installed.